Battery charger



April 2 1951 A. M. SALAZAR v?,549,854

BATTERY CHARGER Filed July 20, 1949 I 2 Sheets-Sheet l INVENTOR AL FEE D M- SA LAZAR ATTORNEY April 1951 A. M. SALAZAR 2,549,854

BATTERY CHARGER izzmffl Patented Apr. 24, 1951 UNITED STAT ES BATTERY CHARGER.

Alfred M. Salazar, Babylon, Y., assignor to Federal Telephone-and Radio Corporation, New York, N. Y., a. corporation of Delaware Applica ion Jul 20,1 9. Serial No.1.05fl

This invention relates to battery chargers and more particularly to improvements in time and voltage controlled battery charging systems.

The value of a charging current that can be supplied to a lead cell battery at any given time during the charge is dependent upon the state of charge of the battery. 'If current in excess of this value is forced into the battery, it overheats and gassing occurs. The creation of gassing, besides representing a loss in energy, also means that a scrubbing action is produced, a process which slowly removes the active material from the cell plates resulting in reduced batterylife.

Keeping the voltage applied across the battery constant provides the quickest method of charging to obtain maximnm eificiency and minimum gassing. The principal disadvantage of this method is that it requires an initial charging current of 500 amperes for a 500 ampere-hour battery. As this current is extremely high, it

requires large, expensive charging equipment.

As most industrial material handling equipment is operated on the basis of an eight hour shift operation, the time available for rechargthe initial charging current required and the lower cost of the equipment'to supply it. Accordingly, users o th eq ment equi e char n n t capable of charging one or two batteries within the allotted time without manual operation of the controls by an operator.

Battery chargers have been previously deve' oped capable of charging alead storage battery at a relatively high rate until the predetermined voltage is reached and then automatically reducing the charging rate to therfinishing value which is maintained for a definite and predetermined time. In my application Ser. No. 683,314 filed July 13, 1946 now "Patent No. 253L472, issued November 28, '19 50 'I disclosed a two rate battery charger utilizing a single high current rated contactor with a low rated contactor capable of charging either lead or Edison batteries.

It is an object of my present invention to provide a charger using a single alternating current supply circuit and rectifier means to automatically charge in sequence a plurality of batteries at'high and low rates of charge.

Another object of my invention is to provide a charger utilizing a single high current rated contactor which, when initially set into oper- .2 ation, will sequentially charge two lead batteries with both high and low rates of charging and alternatively will sequentially charge two Edison batteries at high rates of charge for predetermined rates of time.

It has been found that the voltage at which excessive gassing occurs in lead storage batteries is approximately 2.3? volts per cell at 77- F. It is obvious that the higher the rate of; charge, the sooner the battery reaches this gassing voltage. It has been found that the most satisfactory results are obtained when a battery is charged up to the gassing point (approximately 85% of full charge), at the high rate and then charged at the low rate for about three hours to brin not be detrimental to the battery,

According to one of the features of my invention a voltage sensitive relay is used to introduce a resistance into the battery charging circuit when the battery potential reaches the gassing point, thereby loweringthe rate of charge.

A timing device regulates the duration of the low rate of charge. At the expiration of the charging period a recycling control, comprising another timing device, is used to automatically substitute a second battery in place of the first one and to repeat the cycle of high and low rates of charge for the second battery.

The above-mentioned and other features and objects of this invention and the manner of attaining them will become more a parent and the invention itself will be best understood, by reference o the o lowin des i on of a nibodiment of the invention taken in conjunction with the om an draw ngs, W er im i i a hemat e of he c rging means connected with ,a single phase alternating source of supply.

Fig. 2 is a schematic view of a modification of thebattery charger circuit of Fig. '1.

Referring to Fig. '1 there is shown therein a source of alternating current I connected to the primary of transformer T through the doublepole-single-throw switch '2 and the main alternating current supply lines 3 and 4. The sec ondary of transformer T is connected to the rectifier bridge 5 which is connected inturn through the output lines 6 and I to the batteries to be charged.

A high-rate contactor 9 is provided which, in its normally open position, opens circuit line I.

This open circuit is bridged by a low rate resistor 10, one end of which is connected to line 4 on the power side of the contactor 9, and the other end of which is connected through the armature of a circuit-making relay H and a contact 12 of this relay which is in turn connected to line 4 on the transformer side of the contactor Q. The normally open relay I I has two contacts, |2 and 25, and is closed Whenever the charging circuit is operative, as will be subsequently shown.

Voltage sensitive relay 8 is connected across the output of rectifier bridge to control the duration of the high rate of charge. This relay switches the circuit to a low rate of charge when the battery being charged reaches a predetermined voltage level. In its normally open position against its front contact 24 the armature of relay 8, which is connected through line 3 to supply line 3, rovides a closed circuit for the actuating coil of the high rate contactor 9 through line 4, the low rate resistor iii, the armature of relay H and the contact 25 of relay H which is connected to the front contact 24 of relay 8 through the actuating coil of contactor High rate contactor 9 is thereby closed, shunting the low rate resistor to and placing the primary of the transformer T directly across the alternating current source Contactor 9 is maintained in this closed position by the potential drop across the primary of transformer T through contact l2 and the armature of relay ii, contact 25 of relay l, the actuating coil of the high rate contactor, the armature and front contact 24 of relay 8, and line i3 which is connected to supply line 3.

The low rate of charge is initiated by the closing of voltage sensitive relay 8 which opens the circuit 2 of the actuating coil of contactor Q, thus eliminating the shunt across the low rate resistor H] in the primary circuit of transformer T.

Two electric timing relays, I4 and i5, are provided to control the duration of the low rate of charge. These relays may have electric motors associated with timing devices which, when set to any predetermined time interval, will close upon expiration of such interval the associated relay armature against its back contact. After the motor has been operated for the predetermined interval of time, the armature will be released against its front contact.

When the voltage sensitive relay 9 is actuated. and its armature is pulled against its front contact 26 the two electric timers are connected in common through line |3 to line 3 of the main alternating current supply circuit. The other side of electric timer l4, when preset, is connected through its back contact 21 and its armature through line I6 to line 4 of the alternating current supply circuit. The other side of electric timer l5, when preset, is connected through its back contact 28 and its armature, the front contact 29 and armature of timing relay l4, and line it to line 4 of the alternating current sup-ply circuit. It may be seen that the motor of timing relay l5 cannot operate until timing relay i4 is open and its armature is against its front contact 29. The back contact 2? of timing relay I4 is connected through the actuating coil of a time delay relay I! and through the actuating coil of circuit-making relay H to line 3.

Time delay relay I! may be a copper slug or ratchet relay with a slow travelling time; or it may be a thermal time delay having a heating element in place of the actuating coil as shown in Fig. 2. This relay has an armature and two contacts, both of which connect the voltage sensitive relay 8 to the output of the rectifier bridge. While the armature of relay ii is travelling from one contact to the other the voltage sensitive relay 8 is connected from the output circuit of the rectifier bridge for a brief interval of time in order to allow the armatureof relay'S to return to its normally open position while the output circuit is being shifted from a first to a second battery.

The break-before-make battery contactor |8 connects positive output line 7 to a first battery through lead 23 while in its normally open position, and to a second battery through lead 2| when actuated. The negative poles of both batteries are connected in common to negative output line if through lead IS. The coil of contactor it is connected to the back contact 28 of timing relay [5 through the coil of the circuit-making relay II to line 3. It is thus apparent that if either or both of the timing relays are preset, either the time delay relay ll or the battery contactor it will be actuated through the coil of the circuit-making relay ii. Conversely if neither timing relay is preset the coil of relay i will not be actuated and the main alternating current supply source will be disconnected from the transformer.

Single-pole single-throw switch 23 is provided to connect the front and back contacts of the voltage sensitive relay 8 in order to convert the circuit for charging Edison batteries, which require only the high rate of charge for a predetermined time interval.

In the arrangement shown in Fig. 1 the positive poles of the two lead batteries to be charged are connected to leads 20 and 2| respectively and the negative poles are connected to the common negative lead |9. Electric timing relays l4 and I5 are set to the desired time intervals of the low rate charge of the batteries connected to leads 2E and 2| respectively. The setting of the electric timers will close the armatures of the timing relays l4 and i5 against their respective back contacts 27 and 28. switch 2 places the potential difference between lines 3 and i across the actuating coil of circuitmaking relay H through the actuating coil of relay ll, the armature and back contact 21 of relay i2 and line IS. The armature of relay it will close against its contacts l2 and 25, actuating the coil of the high-rate contactor 9 through line 4, the low rate resistor It), the armature and contact 25 of relay II, the coil of contactor 9, the back contact 24 and the armature of voltage sensitive relay 8, line l3, and line 3. The closing of the high rate contactor 9 shunts the low-rate resistor and places the potential drop of the main power supply circuit across the primary of transformer T. This potential drop maintains contactor through contact |2 and the armature of relay H, the coil of contactor 9, the back contact 24 and the armature of relay 8, and line IS. The circuit will maintain a high-rate condition of charge until the last mentioned circuit is opened by the actuation of voltage sensitive relay 8.

The voltage sensitive relay 8 will close when the battery being charged across the leads l9 and 20 reaches a predetermined potential limit. The closing of relay 8 against its back contact 26 opens the high-rate contactor 9, placing the low-rate resistor H), which is no longer shunted,

Closure of the main power Q in a closed position s s-racer in'the main power supply circuit. AtQt'hesa-me- When the armature of the timing relay I is released against its front contact 2 5', the coil of battery contactor i8 is actuated through line I6 the armature and front contact 2% of timing relay I4, the armature and back contact 28 of timing relay I5, and the coil of circuit-making relay II. The closing of battery contactor It will disconnect the first battery from the output circuit and will, in'its place, connect the second battery between leads 2% and I9. At the same time the time delay relay I! will be opened while its armature travels from one of its contacts to the other, for an interval of time sufioient to disconnect the voltage sensitive relay 8 from the output circuit of the rectifier. This allows relay 8 to return to the normally opened position against its back contact 2 thereby closing the high-rate contactor 9 and opening the circuit the timing relay motors to prevent their cperation. The circuit will charge the second. battery at the high rate until it reaches the voltage level requisite to close the armature relay 8 against its front contact, opening the high-rate contactor and again placing the Iow -rate re sistor in the main. powcr supply circuit. closure of relay 8 will also set the motor of tim-- ing relay it: into operation through its own back contact 2%, the front contact 26 of timing relay I4, and line It. The low rate of charge will continue until the timing relay I5 opens after the preset period of time. The opening of this relay disconnects both timing relays from the power supply circuit and also inactivates the coil of relay ll, causing the main power supply to open. A pilot light 22 may be connects-cl between the front contact as of timing relay l5 and line 3 to indicate the completion of the battery charge.

It is apparent that this circuit be used to charge a single battery with its positive pole connected to either lead as or provided the corresponding electric timer is preset. It is equally apparent that the circuit cannot be put into operation without the presetting of either or both of the electric timers i and In order to charge Edison batteries, which require a single high rate of charge for a predetermined rate of time, single-pole throw switch 23 is closed connecting the front and back contacts of relay 8. This switch keeps the highrate contactor 9 closed regardless of the position of voltage sensitive relay 8. With the two batteries connected and the two timing relays preset, timing relay i l will be placed across the power supply circuit, thetime delay relay ll will be in an activated condition and the circuitmaking relay M will be closed. At the expiration of the preset time the armature of timing.

relay It will open against its front contact 29 placing timing relay I5 across the power supply circuit and connecting the second battery to the output by closing battery 'contactor it through the back contact 2% of timing relay i5 and the coil of the circuit-making relay II. Relay Ill will be de-energized. When timing relay I5 openskthe tiniing relaymotorsj the battery con:- Hit-the time delay relay l 'l, 811421 the Gil tactd cuit making relay coil- I I will all be inactivated; disconnecting the transformer from the main-" powe'r'sourc'e.

'At the expiration of the charging period the battery connected to lead 28 may show a slight discharge through the re'c tifier bridge -5 and through the coil of the voltage sensitive relay.

The-energy loss through these circuits, however, is'alinost negligible.

Fig. 2 illustrates a s'imilarbattery charging circuitmodified in the use of component parts and in circuit connections. In this circuit the alter na-ting' current in-put i applied to the primary of a transformer T through a double-pole-singlethrow switch M and the main alternating current supply lines 4| and 42. Line 4| is normally open circuited by the high-rate contactor 4 3.

= itith rough the normally open battery contactors' t9 and 50 respectively.

The actuatin coil of battery contactor 49 has two ends connected respectively to the battery lead 4? and to the frontcontact 5| ofthe trans fer relay armature R3. The actuatingcoil of contactor' Ell has its two ends connected respectively to the battery lead M3 and the back contact 52 of the transfer relay armature R3. Armature R3 of the transfer relay is connected to the negative output lead 45, and consequently the coil of contactor 49 will be energized across the battery connected to leads 4'5 and-41 through the front contact 51 and armature R3 when the transfer relay is actuated, thus placing the batte'ry connected to leads 4-? and 45 across the out put of the rectifier bridge 44'. The coilof con: tactor 59 will be placed across the battery connected to leads 15 and 48 through the front cori- Y tact 52 and the armature Rx of the transfer relay when the relay is in its normally open position. It is apparent that when armature R: is against its back contact 52 the battery connected between loads 48 and 45 will be charged from the rectifier bridge 44 and the battery con nected between leads 4'! and 45 will be disconnected therefrom, inasmuch as contactor 49 cannot be actuated.

The shift from high to low rates of charge is controlled by the voltage sensitive relay 53, the actuating coil of which has one end connected to the negative lead 45 and the other and connected to the bi-metallic armature of time delay thermostat 54. The front contact 55 of the time delay thermostat is connected to the battery lead 4! and the back contact 56 is connected to the battery lead 48. When the time delay thermostat is energized the voltage sensitive relay 53 will be connected across the battery between leads -41 and 45. When the time delay thermostat opens the bi-metallic armature will take an appreciable amount of time to travel to the back-contact 56, thereby disconnecting the actuating coil of the voltage sensitiv relay for a sufficient interval of time for the armature of the voltage sensitive relay 53 to regain its normally auassa.

open position. The time delay thermostat armature then connects the voltage sensitive relay through the back contact 56 across the battery connected between leads 48 and 45.

A double-pole-double-throw selector switch 80 adapts the circuit for charging either Lead or Edison batteries. The two ends of the actuating coil of the high rate contactor 43 are connected to center posts 57 and 58 of the selector switch. When the selector switch is thrown to the Lead side, post is connected'with post 59 which in turn is connected to the main supply line 4| on the transformer side of contactor 43, and post 58 is connected to post 60 of the selector switch which in turn is connecmd to the back contact 6| of the voltage sensitive relay 53. The armature of the voltage sensitive relay 53 is connected to the main supply line 42 while the front contact 15 of this relay is connected to the armature R2 of the transfer relay R.

Two electrical timers E2 and 63, each having an associated relay, are utilized to control the duration of the low rate of charge of the batteries connected to leads 4! and 48 respectively. One side of electric timer 62 is therefore connected to the front contact 64 of the armature R2 and one side of the electrical timer B3 is connected to the back contact 65 of armature R2. The other side of electrical timer 62 is attached to its own back contact 66 and the other side of electrical timer 63 is connected to its own back contact 61. The armature of electrical timing relay 53 is connected to the front contact 68 of electrical timing relay 62; the armature of electrical timing relay 62 is in turn connected to the main supply line 4|. It will thus be seen that electrical timer 63 cannot be operated unless the armature of electrical timing relay 62 is opened and against its front contact 68.

The transfer relay R and the time delay thermostat 54 are connected in parallel between the main supply line 42 and the back contact 56 of the electrical timer 52, and will therefore be actuated whenever electrical timer 62 is pre-set and its associated armature is against its back contact 66.

The low rate resistor 69 is connected between the center post 5'! of the selector switch 80 and armature R1 of the transfer relay. The front contact of this armature is connected to the back contact '56 of electrical timing relay 62; the back contact '5! of this armature is connected to the back contact 61 of electrical timing relay 63.

When the selector switch 80 is thrown to the Edison side. center post 58 is connected to main supply line 42 through post 12.

A pilot lamp i3 may be connected between the back contact 74 of the electrical timing relay 53 and line 42 to indicate the expiration of the charging period.

To operate the charging circuit the positive poles of two lead cell batteries to be charged are connected to leads 4'! and 48 respectively and their negative poles are connected in common to the negative lead 45. The selector switch 80 is thrown to the Lead position and the two electrical timers 62 and 83 are pre-set to the desired duration of low rate of charge for the batteries connected to leads 41 and 48 respectively.

The pre-setting of electrical timers 62 and 63 will switch their associated armatures against their back contacts 65 and 61 respectively. When the main power switch 40 is closed the transfer relay R is energized and its armatures R1, R2 and R3 are closed against their front contacts 10, 64 and 5l respectively. The time delay thermostat 54 will also become energized and its bi-metallic armature will close against its front contact 55. The high-rate contactor 43 will immediately close, its coil being actuated by the current from the supply line 42, the armature and back contact 6! of the voltage sensitive relay 53, posts 60 and 58 of the selector switch 80, the high rate contactor coil, post 51 of the selector switch, low rate resistor 69, the armature R1 and the front contact 10 of transfer relay R, the back contact 56 and the armature of electrical timing relay 62 which is connected to the supply line 4|. Closure of the high rate contactor will shunt the circuit of the low rate resistor 69 and the contactor will be maintained in its closed position by the potential developed across the primary of transformer T. Inasmuch as armature R3 is against its front contact 5|, the battery connected to lead 41 will close the battery contactor 49 and the battery will be charged at the high rate.

The high rate of charge will continue until the battery potential reaches the predetermined limit and actuates the voltage sensitive relay 53 through the front contact 55 of the time delay thermostat 54. The closing of this relay opens high rate contactor 43 and the main supply current will then flow through posts 59 and 51 of the selector switch 80, the low rate resistor 59, the armature R1 and the front contact 18 of the transfer relay, and the back contact 56 and the armature of the electrical timing relay 62, thus introducing the low rate resistor into the main supply circuit and reducing the current flow.

At the same time, the closure of the voltage sensitive relay 53 against it front contact '15 will cause the motor of the electrical timer 62 to operate through its associated back contact 66 and the front contact 64 and armature R2 of the transfer relay R. The low rate of charge of the battery connected to lead 4"! will continue for the interval of time pre-set on electrical timer 62.

At the expiration of this time interval the armature of electrical timing relay 52 will open against its front contact 68 thereby de-energizing the transfer relay R and the time delay thermostat 54.

The opening of the armature R3 against its back contact 52 will open-circuit the contactor 49 and close the circuit of contactor 50 across the battery connected to lead 48, thereby substituting this battery for the battery connected to lead 41 in the out-put circuit of the rectifier. Inasmuch as the bi-metallic armature of the time delay thermostat 54 will take an appreciable amount of time to travel from its front contact 55 to its back contact 56, the voltage sensitive relay 53 will be temporarily disconnected and its armature will return to its normally open position against its back contact 6|. The closing of this relay will close the circuit of the high rate contactor 43 and will reinstitute the high rate of charge for the second battery.

When this battery reaches its predetermined potential limit the voltage sensitive relay 53 will close, placing the charging circuit in its low rate condition and setting electrical timer 63 into operation through the armature and front contact 15 of voltage sensitive relay 53, arma- '9 ture R2 and its back contact 55, the back contact 61 and armature of electrical :timing relay 63, and :the front contact J38 and armature-of electrical timing relay 62. At the expiration of the interval of time preset on electrical-timer-EB, its-armature will open against its frontcontact F'M, lighting pilot lamp 113. to indicate thatthe charging circuit is no :longer connected tothe alternating current in- :put,

When it is'desired to'charge Edison cells the batteries are connected as before and the selector switch at is thrown to the Edison position. The electrical timers t2 "and 53 arepreset to the desired duration of the high rate of charge to be applied to the batteries connected to leads 4'5 and 48 repectively. The circuit is now arranged so that a high rate contactor ts will be closed whenever either one or both of the electrical timers t2 and 63 are in a Dre-set closed condition regardless of the condition of the voltage sensitive relay 53. Inasmuch as Edison batteries are of high voltage, the voltage sensitive relay 53 will remain closed for the entire charging period, so that electrical timers 62 and 63 will operate in sequence along with the respective battery contactors it and 56. The batteries connected to leads t1 and id are therefore sequentially charged at the high rate for the intervals of time pre-set on the respective electrical timers 62 and 63. When the armatures of the two timers are against their front contacts 63 and M the charging circuit will be disconnected as before and the pilot lamp #3 will indicate that the batteries may be removed.

While I have shown several embodiments of the circuit, many variations will be obvious to those skilled in the art, as for example the adaptation of these circuits to three phase current or the addition of other batteries to be changed in sequence. It is to be clearly understood therefore that these descriptions are made only by Way of example and not as limitations to the scope of my invention.

What is claimed is:

l. A battery charger comprising rectifying means adapted for connection to a source of alternating current, a direct current output circuit from said rectifying means, means to alternatively connect a plurality of batteries to said output circuit, means responsive to the battery potential to automatically switch the battery charger from an initial high rate of charge to a lower rate of charge, and means to sequentially actuate said connecting means after each cycle of high and low rate of charge.

2. A battery charger comprising rectifying means adapted for connection to a source of al ternating current, a direct current output circuit from said rectifying means, means to sequentially connect each of two sets of battery cells to said output circuit, means responsive to a predetermined potential of a connected set of battery cells to lower the initial rate of charge of the battery charger, means to automatically actuate said sequential connecting means after a predetermined duration of the lower rate of charge thereby initiating the charging cycle for said second set of battery cells.

3. A high and low rate battery charger adapted to charge two storage batteries in sequence comprising rectifying means, an alternating current input circuit having a resistance, a direct current output circuit for said rectifying means,

ilO

:means to alternatively connect the said two stor- --age batteries to said output circuit, a line contactor responsive t the potential of a connected storage battery to shunt said input circuit resistor when the battery potential is below a predetermined limit, timing means to control the time interval of charge after ach connected storage battery reaches the said predetermined potential limit, means responsive to the said timing means to actuate said connecting means at the expirationof said time interval of charge of the first of said two storage batteries, thereby connecting said second storage battery for acharging cycle.

l. A two-rate batterycharger adapted to charge two storage batteries in sequence comprising rectifying means adapted for connection to an alternating current source, a direct current output circuit from said rectifying means, means to alternatively connect said two storage batteries to said output circuit, means responsive to a predetermined potential of a connected battery to reduce the initial high rate of charge, timing means to control the time interval of the reduced charging rate, means to actuate said connecting means at the expiration of said timed interval of reduced rate of charge of the first storage battery, and means to disconnect the batteries at the expiration of the timed interval of reduced rate of charge of the second storage battery.

5. A two-rate battery charger adapted to charge in sequence a first and a second storage battery comprising rectifying means adapted for connection to a source of alternating current, a direct current output circuit for said rectifying means, means to sequentially connect the first and the second storage battery to the said output circuit, voltage responsive means to reduce the rate of charge when the connected battery is above a predetermined level of potential, a first timing means to control the time interval of reduced rate of charge of said first battery, means responsive to the expiration of said time interval to actuate said connecting means to disconnect said first battery and connect said second battery to said output circuit, a second timing means to control the time interval of reduced rate of charge of the said second battery, means responsive to the expiration of the second time interval to disconnect said battery charger from said alternating current source.

6. A two rate battery charger adapted to charge in sequence a first and a second storage batter: comprising rectifying means, an alternating current input circuit having a resistance, a direct current output circuit for said rectifying means, means to sequentially connect the said two storage batterles to said output circuit, a voltage sensitive relay responsive to a predetermined potential of a connected battery, a line contactor responsive to said voltage sensitive relay to shunt said input circuit resistor when said battery potential is below said predetermined potential, a first timing means to control the time interval of charge after the first storage battery reaches said predetermined potential, a first means responsive to the expiration of said time interval to actuate said connecting means to disconnect said first battery and connect said second battery to said output circuit, a second means responsive to the expiration of said time interval to de-energize said voltage sensitive relay for a time sufficient to return the relay to its low battery potential condition, a second timin means to con- 11 trol the time interval of charge after the second storage battery reaches said predetermined potential limit, means responsive to the expiration of the second time interval to open said alternating current input circuit.

ALFRED M. SALAZAR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 836,314 Freund Nov. 20, 1906 1,283,380 Watson Oct. 29, 1918 Number Number Name Date Ogden June 29, 1920 Ogden Sept. 26, 1922 Addicks Sept. 3, 1929 Marrison Aug. 14, 1934 Wetzer Oct. 19, 1937 Agnew et a1 Jan. 4, 1938 Exner July 4, 1939 Amsden Dec. 31, 1940 Strong Oct. 22, 1946 FOREIGN PATENTS Country Date Great Britain Feb. 11, 935 

